/*This file is part of the FEBio source code and is licensed under the MIT license
 listed below.
 
 See Copyright-FEBio.txt for details.
 
 Copyright (c) 2021 University of Utah, The Trustees of Columbia University in
 the City of New York, and others.
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:
 
 The above copyright notice and this permission notice shall be included in all
 copies or substantial portions of the Software.
 
 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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 SOFTWARE.*/



#pragma once
#include "FEViscousFluid.h"

//-----------------------------------------------------------------------------
// This class evaluates the viscous stress in a Bingham plastic fluid

class FEBIOFLUID_API FEBinghamFluid : public FEViscousFluid
{
public:
    //! constructor
    FEBinghamFluid(FEModel* pfem);
    
    //! viscous stress
    mat3ds Stress(FEMaterialPoint& pt) override;
    
    //! tangent of stress with respect to strain J
    mat3ds Tangent_Strain(FEMaterialPoint& mp) override;
    
    //! tangent of stress with respect to rate of deformation tensor D
    tens4ds Tangent_RateOfDeformation(FEMaterialPoint& mp) override;
    
    //! tangent of stress with respect to temperature
    mat3ds Tangent_Temperature(FEMaterialPoint& mp) override { return mat3ds(0); };
    
    //! dynamic viscosity
    double ShearViscosity(FEMaterialPoint& mp) override;
    
    //! bulk viscosity
    double BulkViscosity(FEMaterialPoint& mp) override;
    
public:
    double  m_mu;       //!< shear viscosity at infinite shear rate
    double  m_tauy;     //!< yield stress
    double  m_n;        //!< exponential-law coefficient
    
    // declare parameter list
    DECLARE_FECORE_CLASS();
};
